السالم عليكن ورحمة هللا وبركاته إعداد وتقدين : أبو احمد WWW.PALNURSE.COM BLOOD PRESSURE WHAT IS BLOOD PRESSURE? Blood pressure refers to the force (pressure) with which the blood presses against the walls of the blood vessel. All blood vessels--large or small, artery or vein--have blood pressure. However, the term blood pressure normally refers to the blood pressure of a major artery. Unlike the other vital signs discussed previously, it takes two numbers--the systolic pressure and the diastolic pressure--to describe this vital sign. Blood pressure is normally measured in millimeters of mercury (mm Hg). "Millimeters of mercury" is a standard unit for measuring pressure. It refers to how high a force (pressure) would cause a column of mercury (chemical symbol Hg) to rise in a tube. Figure 5-1 gives the general idea. The greater the pressure, the more mercury is forced up the tube. Figure 1. "Millimeters of mercury" as a measure of pressure. WHAT ARE SYSTOLIC AND DIASTOLIC PRESSURES? Basically, the systolic pressure is the greatest pressure that the blood exerts against the walls of the blood vessel while the diastolic is the lowest pressure that the blood exerts against the walls of the vessel. A person's blood pressure depends upon the force of the heart's pumping action, the degree to which the blood vessel will stretch, and the amount of blood in the blood vessel. a. Systolic. The arteries are under the greatest pressure when the heart pumps blood into them. The extra blood that is forced into the arteries make them stretch. (1) In a normal adult male, the systolic pressure should be between 100 and 140 mm Hg, inclusive. (Inclusive simply means to include the ends of the range. Systolic pressures of 100 and of 140 are within normal range.) (2) In a normal adult female, the systolic pressure should be between 90 and 130 mm Hg, inclusive. b. Diastolic. The arteries are under the least pressure from the blood when the heart is at rest (between pumps or beats) and the arteries have returned to their normal size. (1) In a normal adult male, the diastolic pressure should be between 60 and 90 mm Hg, inclusive. (2) In a normal adult female, the diastolic pressure should be between 50 and 80 mm Hg, inclusive. WHAT FACTS AFFECT A PERSON'S BLOOD PRESSURE? There are several factors that can affect a patient's blood pressure. Some are only temporary; others are long-term effects. A condition in which the blood pressure is considerably above normal is called "hypertension." If the blood pressure is too low, it is called "hypotension." a. Condition of Cardiovascular System. A primary factor influencing a patient's blood pressure is the condition of his cardiovascular system (heart and blood vessels). (1) If a patient's heart is not pumping blood with enough force, his blood pressure will be low. This will decrease the rate that blood is circulated throughout the body. Slow blood circulation may result in certain parts of the body (especially the brain) not receiving enough oxygen since oxygen is carried by the blood. (2) If a patient's heart is pumping with too much force, his blood pressure will be high. If an artery has a weak spot, the force of the systolic pressure may be enough to rupture the artery and allow blood to escape. (3) If a patient's arteries loose part of their elasticity, such as in patients who have arteriosclerosis (hardening of the arteries), the patient's blood pressure will be higher, since the artery walls stretch less and cannot relieve as much pressure. b. Age. A person's blood pressure readings tend to increase as he grows older. c. Gender. As indicated in paragraph 5-2, men tend to have higher blood pressure than women of the same age. d. Physical Fitness. People who are physically fit tend to have more normal blood pressure than people who are "out of shape." e. Obesity. People who are very overweight usually have higher blood pressure than they would if their weight were closer to their ideal weight. f. Pain. Pain is a type of body defense that lets the brain know that something is wrong. The brain may respond to pain by increasing the rate and strength of heartbeats. The increased rate increases the amount of oxygen available to the muscles for producing energy. It also results in an increased blood pressure. g. Emotion. Fear, worry, excitement, and similar emotions can result in a higher blood pressure. The brain may react to these emotions in basically the same way that it reacts to pain. h. Gravity. If a person is standing, the blood pressure of the arteries in the lower part of the body will be greater than the pressure in the upper part of the body. i. Exercise. A person's blood pressure is greater during and just after exercising because the heart beats faster in order to supply additional oxygen to the muscles. j. Disease. Almost any disorder that affects the arteries or the renal (kidney) system will result in a higher blood pressure. Diseases that weaken the heart will usually result in a lower blood pressure. k. Drugs. Drugs designed to strengthen the actions of the heart, such as digitalis, will cause the patient's blood pressure to rise. Drugs that cause the arteries to become smaller in diameter (called vasoconstrictors) will also cause the patient's blood pressure to rise. Drugs that cause the patient's arteries to become larger in diameter (called vasodilators) will decrease blood pressure. l. Eating. A person's blood pressure is usually elevated (increased) while he is eating and for a while after he finishes the meal. m. Bleeding. Serious bleeding (hemorrhaging) reduces the amount of blood in the body's circulatory system and thus reduces blood pressure. WHAT EQUIPMENT IS NEEDED TO MEASURE A PATIENT'S BLOOD PRESSU RE? You will need a sphygmomanometer (sfig'-mo-mah-NOM-e-ter) and a stethoscope (STETH-ah-skop). Figure 5-2. Sphygmomanometers. A Portable mercury sphygmomanometer. B Portable aneroid sphygmomanometer. a. Sphygmomanometer. The sphygmomanometer (figure 5-2) is usually called the "blood pressure cuff." There are several different types of blood pressure cuffs in use. Some are made to be attached to a wall (next to a patient's hospital bed, for example), but most are portable. All blood pressure cuff devices work basically in the same way and have the same parts--a bladder, a handbulb with release valve, a tube connecting the handbulb to the bladder, and a gauge (either mercury or aneroid) for measuring pressure. (1) Bladder. The bladder (also called the "cuff") is a long rubber bag about 6 inches wide and 24 inches long that is covered with fabric. The bladder is wrapped around the patient's arm and filled with air when taking the patient's blood pressure. Parts of the fabric are made of non-slip material, such as Velcro. When the fabric is overlapped, the two pieces of fabric adhere to each other and will not slip when the bladder is inflated. Some sphygmomanometers use snaps or other devices to secure the bladder instead of non-slip fabric. (2) Handbulb. The handbulb is a device for inflating the bladder. When squeezed, the handbulb forces the air through an opening connected to the tubing. When the bulb is released, it refills with air from the environment. The handbulb is designed so that air from the tubing cannot flow back into the handbulb. (3) Rubber tubes. One tube connects the bladder and handbulb. Air that is forced out of the handbulb travels through the tube and enters the bladder. A second tube connects the bladder and the gauge.. (4) Release valve. The release valve (screw) is a device for releasing air from the bladder. It is located between the handbulb and the tubing. One hand can operate both the handbulb and the release valve easily. The valve is controlled by a screw. When tightened, no air escapes. When unscrewed fully, the air escapes rapidly. (Note: The screw does not separate from the apparatus. "Unscrewed fully" means the screw is turned so that air will escape as fast as possible.) The screw can also be turned to any position between completely closed and full release. In this way, you can let air escape from the bladder as quickly or as slowly as you wish (5) Gauge. The gauge measures the air pressure in the bladder. There are two types of gauges--the mercury gauge and the aneroid gauge. (a) Mercury. The mercury gauge has a column of mercury in a glass tube. The column of mercury measures the air pressure in the bladder. The higher the pressure of air in the bladder, the higher the column of mercury. The height of the column of mercury is determined using a scale to the side of the tube containing the mercury. Usually there is a scale on each side of the glass tube in order to make it easier to read the height of the column. As air is released from the bladder, the air pressure drops and the column of mercury becomes shorter. (b) Aneroid. The aneroid gauge is circular and has a dial. The greater the air pressure in the bladder, the farther the needle on the dial rotates. A scale on the dial is equivalent to the scale of the mercury gauge. Both scales measure the force of air pressure in the bladder in terms of mm Hg. As the air pressure is released, the needle moves in a counter-clockwise direction. The gauge will normally be designed so that it can be attached to the bladder. This frees the person taking the blood pressure from having to hold the gauge in one of his hands. b. Stethoscope. The stethoscope is an instrument used for listening to sounds produced within the body. A stethoscope consists of a diaphragm, metal and rubber tubing, and earpieces (figure 5-3). (1) Diaphragm. The diaphragm is normally a flat metal disk that is placed on the body area being examined. The diaphragm will pick up sounds produced within the body such as the heartbeat and breathing sounds. Sometimes a bell-shaped listening device is used instead of a flat disk. Some stethoscopes have combination (both flat disk and bell) listening devices. (2) Tubing. The hollow and metal tubes transmit the sounds from the diaphragm to the earpieces. The rubber tubing provides flexibility. Figure 3. Stethoscope. (3) Earpieces. The earpieces are twisted metal tubes with plastic ends. The plastic pieces protect the ears from the metal. The twisting helps to improve the quality of sound heard through the stethoscope. The stethoscope should be worn with the earpieces forward (figure 5-4) to help prevent the sounds picked up by the diaphragm from being distorted. Figure 4. Earpiece of stethoscope in place for use. HOW DOES THE AIR PRESSURE INSIDE THE BLADDER PROVIDE INFORMATION ABOUT THE BLOOD PRESSURE? Paragraph 5-1 stated that blood pressure is the force with which the blood pushes against the walls of the blood vessel. However, paragraph 5-3a(5) states that the gauge on the sphygmomanometer measures the air pressure inside the bladder! a. Indirect Measurement. Some things cannot be measured directly without difficulty. For example, the height of a building can be measured by climbing to the top of the building, holding on to one end of a very long tape measure, and dropping the other end to a friend on the ground who reads off the height. This method may work for a building that is not very high, but is not recommended for determining the height of the Empire State Building. The height of a building, however, can be determined indirectly, such as by measuring its shadow. (Method: Put a stick in the ground so that it is straight up and down. Measure the height of the stick, the length of the stick's shadow, and the length of the building's shadow. The height of the building is equal to the length of the building's shadow times the height of the stick divided by the length of the stick's shadow.) b. Blood Pressure Measurement. Just as the height of the building was determined by measuring something else (its shadow), the pressure of the blood at its highest (systolic) and normal (diastolic) levels can be determined by measuring the air pressure in the bladder. (1) When the bladder is first placed around the arm and not inflated, the artery beneath the bladder functions normally (figure 5-5 A ). (2) When the bladder is inflated, the bladder squeezes the arm. If the bladder is inflated to a pressure greater than the systolic pressure of the artery, the artery beneath the bladder will collapse (figure 5-5 B ). The artery will remain collapsed, thus shutting off blood flow below the bladder, even when there is a heartbeat. Thus, when there is no blood flow in the artery below the bladder, you know that the air pressure in the bladder is greater than the systolic blood pressure. (3) When the bladder is inflated to a pressure that is less than the systolic pressure but greater than the diastolic pressure, blood will flow beneath the bladder only when the (blood) pressure within the artery is greater than the (air) pressure within the bladder. This occurs when the force of the heartbeat increases the pressure within the artery. Once the additional force of the heartbeat has passed (the artery returns to diastolic pressure), the artery will collapse again (figure 5-5 C ). Thus, when blood suddenly passes through the artery beneath the bladder, stops, starts again, and stops again, you know that the pressure within the bladder is less than the systolic pressure but more than the diastolic pressure. (4) If the bladder is inflated, but the pressure within the bladder is less than the lowest level of pressure within the artery (diastolic pressure), then the bladder cannot collapse the artery. The pressure of the bladder may interfere somewhat with the blood flow, but it cannot stop the blood flow (figure 5-5 D ). Thus, when the blood continues to flow through the artery beneath the bladder without stopping, you know that the pressure within the bladder is less than the lowest (diastolic) pressure of the blood within the artery. A Artery without the bladder--artery expands during heartbeat, returns to normal. B Air pressure in the bladder is greater than the systolic pressure--the artery stays collapsed. C Air pressure in bladder is between systolic pressure and diastolic pressure--artery collapsed except during heartbeat. D Air pressure in bladder is less than diastolic pressure--artery does not collapse. Figure 5. Effects of an inflated bladder on an artery. HOW DO I TAKE A PATIENT'S BLOOD PRESSURE? Use the following procedures when taking a patient's blood pressure. a. Gather Materials. You will need the following items: Sphygmomanometer. Stethoscope. Cotton-tipped applicators (swabs)--at least 8. Disinfecti ng solution (70% alcohol solution). Watch or clock with second hand. Pen or pencil. Form or note pad on which to write. b. Verify the Patient's Identity. Make sure that you are preparing to take the blood pressure of the proper person. c. Set up Equipment. If you have a portable mercury sphygmomanometer, set up the gauge so that it will be at about eye level. If you are using an aneroid gauge, position yourself or the patient so that the gauge will be about eye level when you read it. You can read a gauge easier and more accurately when it is at eye level. d. Clean Earpieces. Wet one swap with the alcohol disinfecting solution. Clean the inside of one plastic earpiece of the stethoscope with the swab and discard the swab. Wet another swab, clean the outside of the plastic earpiece, and discard that swab also. Repeat the procedure for the other plastic earpiece. e. Position the Patient. Have the patient to position himself in the desired position. (1) The blood pressure is normally taken using the patient's upper arm. The patient can stand, sit, or lie down. Normally, the patient will sit with his arm resting on a table or lie down with his arm resting on the bed, cot, or ground. (2) Sometimes, the physician orders that the patient's blood pressure be taken on his thigh instead of on his arm. (The patient's arms may be injured or amputated, for example.) If the blood pressure is to be taken using the thigh, have the patient to lie on his abdomen. If the patient cannot lie on his abdomen, have him to lie on his back with his knees flexed. f. Expose the Site. Have the patient expose the site to be used (upper arm or thigh). Assist the patient as needed. The patient may need to remove a long sleeve shirt or lower his pajama bottoms. The bladder must be placed over the patient's flesh, not his clothing. Rolling a shirt-sleeve or pants leg up could create a tight area above the site where the bladder is applied. This extra tightening could cause the blood pressure readings to be inaccurate. Therefore, it is better to remove a long sleeve shirt or pants rather than rolling them up. g. Explain Procedure to Patient. Briefly tell the patient what you are going to do. The explanation can be combined with instructing the patient to expose the site where the bladder will be applied. Warn the patient that his arm (leg) may be uncomfortable while the bag (bladder) around his arm (leg) is inflated, but reassure the patient that the discomfort will only last 1 or 2 minutes. h. Prepare Bladder. Make sure that the bladder is completely deflated. If air is present in the bladder, open the release valve, force the air out of the bladder, and close the valve. i. Prepare Gauge. If a mercury gauge is being used, place the gauge where it can easily read, yet not in the way. If an aneroid gauge is being used, attach it to the bladder. j. Position Patient's Limb. (1) If the bladder is to be applied to the patient's upper arm and there is a support for the patient's arm (bed, table, ground, etc.), have the patient to extend his arm in a palm up position. The arm should be about the same level as his heart. (2) If the bladder is to be applied to the patient's upper arm but there is no support for his arm, tuck his wrist under your arm so that you will be supporting his arm and keeping it steady. (3) If the bladder is to be applied to the patient's thigh, the patient should remain lying on his abdomen or lying on his back with his knee flexed. k. Wrap Bladder Around Limb. (1) If the upper arm is being used, wrap the bladder around the upper arm. The non-slip material or buckles of the bladder should be on the outside of the bladder, not next to the patient's skin. The bottom edge of the bladder should be one to two inches above the elbow (figure 5-6). (2) If the thigh is being used, wrap the bladder around the middle of the thigh (figure 5-7). A somewhat larger and longer bladder is normally used when the blood pressure is taken in the thigh. Figure 6. Placement of bladder on upper arm. Figure 7. Placement of bladder on thigh. (3) Wrap the bladder firmly around the limb. Overlap the fabric and make sure it will not slip (Velcro to Velcro, fasten buckles, tuck fabric end under bladder, etc.). (4) If an aneroid gauge is being used, wrap the bladder so that the gauge is aligned with the palm of the hand if the arm is used and with the kneecap if the thigh is used. Positioning the gauge in this manner will make it easier for you to read the dial. l. Locate Pulse. Put the earpieces of the stethoscope in your ears (plastic tips forward) and use the diaphragm to find the patient's pulse. (1) If the upper arm is being used, you will use the brachial pulse found just below the crease on the inside of the elbow (figure 5-8). Figure 8. Locating brachial pulse. A Side view. B Top view (2) If the thigh is being used, use the popliteal pulse just above the crease on the inside of the knee. (3) If you are using a combination stethoscope (both disk and bell) and you cannot hear anything, find the lever near the diaphragm and flip it. This will change the source of sound input from the bell to the disk. m. Tighten Screw. Make sure that the valve is completely closed so that the air cannot escape. n. Inflate the Bladder. Inflate the bladder (figure 5-9) by squeezing and releasing the handbulb. Listen to the patient's pulse and watch the gauge as you pump up the bladder. When you can no longer hear the pulse beat, note the reading on the gauge. Then pump the handbulb again until it reads 10 mm Hg higher than it did when the pulse disappeared or until the pressure of 140 mm Hg is reached, whichever is greater. Figure 9. Inflating the bladder. CAUTION: Do not inflate the bladder to a pressure greater than 200 mm Hg. If the pulse can still be heard at 200 mm Hg, deflate the bladder (unscrew the valve) and remove the bladder from around the patient's arm or thigh. Then notify your supervisor of the problem o. Listen for Pulse. Once you have inflated the bladder to the desired pressure (140 mm Hg or higher, depending upon when the pulse disappeared) listen briefly to make sure that you cannot hear the pulse beat below the bladder. (1) If you cannot hear the pulse, then the air pressure inside the bladder is greater than the systolic pressure of the blood. (The bladder is, in effect, now a tourniquet.) You are now ready to begin releasing the air from the bladder. (2) If the pulse can still be heard, inflate the bladder until the pulse disappears, then inflate it an extra 10 mm Hg of pressure. Do not inflate above 200 mm Hg. p. Release Air Slowly. Watch the gauge closely and listen through the stethoscope as you release air from the bladder. Air is released from the bladder by rotating the release valve (screw) counterclockwise (figure 5- 10). The more the screw is turned, the larger the opening and the faster the air escapes. You want the air to escape slowly enough so that you can tell at what pressure reading the pulse reappears, but fast enough that the continued pressure does not harm the patient or cause unnecessary discomfort. Figure 10. Rotating the screw counterclockwise to release pressure. (1) The process of taking a patient's blood pressure (beginning at the time you start inflating the bladder and ending at the time you completely release the pressure) should take less than two minutes. Do not leave an inflated bladder wrapped around the patient's limb for more than two minutes. (2) If you are having problems that will result in going over the two minute mark, deflate the bladder, remove the bladder from around the patient's limb, and wait at least one minute before trying to take his blood pressure again. q. Listen for Pulse. The point at which you hear the pulse beat return is the patient's systolic pressure. Note the reading on the gauge when you hear the first distinct sound of a pulse beat. (1) The markings on the gauge will mark off readings (130, 132, 134, etc.). When you record blood pressure readings, record the reading to the nearest even number (for example, 128 instead of 127). (2) Normally, you will remember the patient's systolic reading and not write it down until you have the determined his diastolic reading also. Writing the number down distracts you from listening to the pulse and watching the gauge as the air continues to escape. r. Continue to Release Pressure. After you identify the patient's systolic pressure, continue to listen to the pulse and watch the gauge as the air continues to escape from the valve. The air should be escaping at a rate that does not require you to adjust the airflow (turn the screw). s. Listen for Last Distinct Sound. As long as the air pressure in the bladder is greater than the diastolic pressure, the artery will collapse after each pulse beat. This makes the pulse have distinct sound. Once the air pressure in the bladder is less than the diastolic pressure of the blood, the artery will remain open at all times. This means that you will be hearing the sound of continuous blood flow in addition to the blood surge caused by the pulse. The pulse will sound muffled and not distinct. The point at which the distinct pulse sound changes to a muffled sound marks the diastolic pressure. (1) Often the pulse will sound louder just before the diastolic pressure is reached. (2) A change in rhythm may also occur at the diastolic level. (3) Sometimes the diastolic is difficult to determine. You may wish to close the valve (turn screw clockwise), inflate the bladder to a point where the pressure is above the diastolic, and release the air at a slower rate than before in order to check yourself. (4) Like the systolic, the diastolic is determined to the nearest even whole mm Hg. t. Release Air. Once you have determined the patient's diastolic pressure, rotate the screw counterclockwise until the valve is opened as far as possible. This will allow the bladder to deflate rapidly. u. Verify Readings, if Needed. If you are not sure that the blood pressure readings (both systolic and diastolic) are correct, squeeze all the air out of the bladder while it is still wrapped around the patient's arm and repeat steps m through t. The blood pressure can usually be checked quickly because you already know the patient's approximate blood pressure readings. This means that you will usually inflate the bladder quickly to a pressure about 10 mm Hg above the first reading, release the air slowly until the first pulse is heard, release air little faster, and then slow the air flow down when you approach the level of the diastolic reading. If the second set of readings is very different from the first, remove the bladder from the patient's limb, force the remaining air out, wait one minute, and take his blood pressure again. v. Record Readings. Record the systolic and diastolic readings. The systolic is written first and is separated from the diastolic by a diagonal line. For example, a systolic of 120 and a diastolic of 80 is written "120/80." Both reading are recorded as whole, even numbers. w. Remove Bladder. Remove the bladder from around the patient's arm or thigh, force the remaining air out of the bladder, and close the valve. x. Assist Patient, If Needed. Assist the patient as needed. For example, you may need to help the patient with his shirt or pajamas. y. Clean Earpieces. If you are not going to continue using the stethoscope, clean the earpieces again. Use the same procedures as previously described in paragraph d. z. Return Equipment. If you will no longer need the sphygmomanometer and stethoscope, return them, along with any other equipment used, to their proper storage area. CAN I TAKE A PATIENT'S BLOOD PRESSURE WITHOUT A STETHOSCOPE? Sometimes the noise level of your work area may make it very difficult to listen to the patient's pulse with a stethoscope or you may not have a stethoscope available. In such cases, use your fingertips (not your thumb) to feel the pulse instead of using a stethoscope to listen for the pulse. The following steps summarize how this procedure is performed. a. Position the Patient. Position the patient so that you can easily take the patient's pulse. b. Locate Pulse. Locate the patient's pulse (inside elbow or knee). c. Place and Inflate Bladder. Wrap the bladder around the patient's upper arm or thigh, as appropriate. (The bladder must be placed between the pulse site and the patient's heart.) d. Inflate Bladder to Starting Point. Inflate the bladder while continuing to feel the patient's pulse. Inflate the bladder until you feel the pulse stop; then inflate it another 10 mm Hg. NOTE: Inflate the bladder to at least 140 mm Hg, but not more than 200 mm Hg.) e. Release the Air Slowly. Turn the valve so that air escapes. Continue to feel for a pulse and continue to watch the gauge. f. Determine Systolic. The systolic is the pressure at which you feel the first pulse beat return. g. Determine Diastolic. The diastolic is the pressure at which the pulse changes to a less distinct (more normal) pulse. The diastolic measurement is only an approximation since it is usually difficult to determine the diastolic using this method. h. Release Air. Open the valve fully in order to relieve the pressure as quickly as possible. i. Verify Readings, If Needed. If you wish to check your results, squeeze the air out of the bladder, close the valve, and repeat the procedure. j. Record Readings. Write the patient's readings (systolic/diastolic) on the form or paper. Remember that both readings are to be even whole numbers. k. Remove Bladder. Remove the bladder from the patient's arm or thigh. Also assist the patient to adjust his clothing or position as needed. l. Return Equipment. If you are not going to take another patient's blood pressure, return the sphygmomanometer to the proper storage area.
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